--- Olin Lathrop <olin_piclist@embedinc.com> wrote:
Yeah, I remember that one. The no-zero radius requirement comes from the
resistivity equation :- R = rho x length/CSA. If CSA --> 0, R goes infinite. As
Olin says, it applies to a probe pressed against the surface (point contact) as
well as an imaginary cylinder of radius "r" drilled thru the block.
Debbie

> I remember working out exactly this case many years ago back in school.  The
> resistance is infinite unless "points" A and B have a non-zero radius.
> 
> > Obviously it can be measured easily in practice by simply placing one
> > ohmmeter probe at A and the other at B.
> 
> Not so obvious.  Try it and you'll see it has a lot to do with the contact
> area at each probe tip.  If the material deforms easily, you will get very
> different answers depending on how hard you press the probes into the
> material.
> 
> 
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